1. Field of Invention
This invention relates to an electronic typewriter having an automatic power-off device, which, when input from a keyboard is interrupted for a predetermined period of time, interrupts automatically all of the power supply to the typewriter, except the power supply necessary for retaining the contents of the memories and for controlling a switch used to cancel the automatic power-off mode.
2. Description of Invention
In conventional electronic typewriters having an automatic power off device, the mode of the typewriter is changed to an automatic power off mode after keyboard operation has been interrupted for a predetermined period of time. It is necessary to operate a special automatic power off cancelling switch, provided in addition to an ordinary main switch, in order to cancel the automatic power off mode. In the automatic power off mode, there is no displaying on the display unit, in addition to the interruption of printing operation.
Thus, the automatic power off mode is indistinguishable, in appearance, from the state wherein the ordinary main switch is turned OFF to interrupt all of the power supply to the electronic typewriter. Consequently, in cancelling the automatic power off mode, the ordinary main switch is liable to be moved to the OFF position accidentally instead of operating the automatic power off cancelling switch. Accordingly, the operation of the ordinary main switch to the OFF position causes erasure of the contents of the memories which have retained data during the automatic power off mode by a backup power source and the return of the print head to the left margin. Disadvantageously, such accidental operation adversely affects the working efficiency.